1. Field of the Invention
In an internal combustion engine provided with a heat control valve in an exhaust manifold, the present invention relates to a seal construction to prevent leakage of exhaust gas through a gap between the heat control valve and the inner surface of the exhaust manifold when the fuel-air mixture in the intake manifold is to be heated.
2. Description of the Prior Art
Generally, in an internal combustion engine, it is known that it is advantageous for the acceleration of vaporization of the gasoline and the combustion of the fuel-air mixture in the cylinders of the engine to heat the fuel-air mixture to some extent before it is supplied to the cylinders. The fuel-air mixture may be heated by hot water from an engine cooling system, but such method requires much time for the fuel-air mixture to reach an appropriate temperature, so that the fuel-air mixture is usually heated by the exhaust gas.
For heating the fuel-air mixture using exhaust gas, a heating chamber is conventionally provided in a portion of the exhaust manifold which is divided from the intake manifold by the top wall of the exhaust manifold, a heat control valve is provided in the heating chamber, and the exhaust gas is contacted with the top wall due to the rotation or swinging of the heat control valve to heat the fuel-air mixture in the intake manifold, or the exhaust gas is prevented from contacting the top wall when heating of the fuel-air mixture is not required.
In such conventional prior art heat control mechanisms, when the heat control valve is rotated or swung to heat the fuel-air mixture, an arm attached to a rotational shaft of the heat control valve is adapted to abut a stopper provided outside of the heating chamber, or, alternatively, the heat control valve is adapted to abut a projection provided within the heating chamber to stop the heat control valve from rotating over the fully closed position thereof.
In a conventional heat control mechanism, however, a space is formed between the heat control valve and the inner surface of the heating chamber for smooth rotation of the heat control valve. Accordingly, even when the heat control valve is fully closed, a part of the exhaust gas flows through the space between the heat control valve and the inner surface of the heating chamber, therefore, it takes much time for the fuel-air mixture to reach an appropriate temperature and fuel consumption is wastefully increased. Further, if a vehicle is operated with an engine in which heating of the fuel-air mixture is not fully completed, the travelling stability of the vehicle is damaged. Moreover, the projecting stopper in the heating chamber above described obstructs smooth flowing of the exhaust gas and causes loss of engine power.